<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h3 + p {
            color: red;
        }
        .title + p{
            color: blue;
        }
    </style>

</head>
<body>
    <div class="box">
        <p>我是p0</p>
        <h3>我是h3</h3>
        <p>我是p1</p>
        <p class="title">我是p2</p>
        <p>我是p3</p>
        <p>我是p4</p>
    </div>
</body>
</html>